Substituted γ‐lactones: On the structural elucidation of the reaction products from 4‐aroyl‐3‐hydroxy‐2(5 H )‐furanones and 1,2‐diamines

The reaction pathway of 4‐aroyl‐3‐hydroxy‐2(5 H )‐furanones 1 with diamines depends on the nature of the amine as well as on the applied reaction conditions. Thus, the reaction of 1a‐d with 5,6‐diamino‐1,3‐dimethyluracil 5 led to the formation of two isomeric Schiff bases 7a‐d and 8a‐d . Conversely type 1 compounds reacted with 4,5‐diaminopyrimidine 9 or 2,3‐diaminopyridine 10 to form the mono acid‐base adducts 11a and 11b respectively. When type 1 compounds were reacted with aliphatic diamines 13a‐d or p ‐phenylenediamine and p ‐xylenediamine, respectively also an immediate formation of acid‐base adducts 15a‐f was observed. The reaction of a number of O ‐methylated type 1 compounds with 1,2‐ethylenediamine afforded the novel seven‐membered ring compounds 18a‐d in good yields. The analogous reaction of O ‐alkylated 1a with o ‐phenylenediamine 2 or 2,3‐diaminonaphthalene gave the expected tricyclic ring systems 19 or 20 .